Downlink Data Transfer Method and Location Update Procedure Execution Method

1. A method of transferring downlink data, the method performed by a Serving Gateway (S-GW) and comprising: transmitting a Downlink Data Notification (DDN) message to a Mobility Management Entity (MME) and a Serving General Packet Radio Service (GPRS) Supporting Node (SGSN), when downlink data arrives at a wireless device in a state where an Idle mode Signaling Reduction (ISR) is activated; receiving a message indicating a refusal of the DDN from any one of the MME and SGSN when the wireless device cannot receive the downlink data since it is in a power saving mode (PSM); and transmitting a paging stop request message to any one of the MME and SGSN upon receiving the message indicating the refusal of the DDN, wherein when the message indicating the refusal of the DDN is received from the MME, the paging stop request message is transmitted to the SGSN, and when the message indicating the refusal of the DDN is received from the SGSN, the paging stop request message is transmitted to the MME.

2. The method of claim 1 , wherein the message indicating the refusal of the DDN is a DDN confirmation message including a cause for the refusal or a message different from a DDN accept message.

3. The method of claim 1 , wherein when the MME supports the PSM of the wireless device but the SGSN does not support the PSM of the wireless device, the message indicating the refusal of the DDN is received from the MME.

4. The method of claim 1 , wherein when the MME does not support the PSM of the wireless device but the SGSN supports the PSM of the wireless device, the message indicating the refusal of the DDN is received from the SGSN.

5. A Serving Gateway (S-GW) comprising: a transceiver; and a controller that: controls the transceiver to transmit a Downlink Data Notification (DDN) message to a Mobility Management Entity (MME) and a Serving General Packet Radio Service (GPRS) Supporting Node (SGSN) when downlink data arrives at a wireless device in a state where an Idle mode Signaling Reduction (ISR) is activated, controls the transceiver to receive a message indicating a refusal of the DDN from any one of the MME and SGSN when the wireless device cannot receive the downlink data since it is in a power saving mode (PSM), and controls the transceiver to transmit a paging stop request message to any one of the MME and SGSN upon receiving the message indicating the refusal of the DDN, wherein when the message indicating the refusal of the DDN is received from the MME, the paging stop request message is transmitted to the SGSN, and when the message indicating the refusal of the DDN is received from the SGSN, the paging stop request message is transmitted to the MME.